Field of the Invention
The present invention relates to a variable compression ratio apparatus, and more particularly to a variable compression ratio apparatus for controlling variation of an engine compression ratio.
Description of Related Art
In general, the thermal efficiency of combustion engines is increased when the compression ratio is high. In the case of a spark ignition engine, the thermal efficiency thereof is increased when ignition timing is advanced to a certain level. However, when the ignition timing of a spark ignition engine is advanced at a high compression ratio, abnormal combustion may occur, thereby damaging the engine. Therefore, there is a limitation on the amount that the ignition timing can be advanced, and the corresponding degradation of output should be tolerated.
A variable compression ratio (VCR) apparatus serves to change the compression ratio of the gas mixture depending on the operational state of an engine. The variable compression ratio apparatus improves fuel efficiency by increasing the compression ratio of the gas mixture when the load on the engine is low. Further, the variable compression ratio apparatus prevents the occurrence of knocking and improves engine output by reducing the compression ratio of the gas mixture when the load on the engine is high.
A conventional variable compression ratio apparatus changes the compression ratio by changing the length of a connecting rod, which connects a piston and a crank shaft. However, because the connection structure between the piston and the crank shaft includes several links, the structure of the variable compression ratio apparatus becomes complicated, inertial mass is increased, and the volume of the package is increased.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.